Astron. Astrophys. 357, L33-L36 (2000)

2. Observations and data reduction

The observations were made in 3 stages. The NIR data (J, K) was collected with the 2.2 m telescope on Calar Alto, Spain in June, 1998 with the IR camera MAGIC. A detailed description of the observation and data reduction will be published separately (Manthey et al., in prep.). The calibration is expected to be accurate within 0.05 mag. By interpolating the coordinates from 30 GSC stars in the field, we estimate the positional uncertainty to be below .

The MIR images at N ( µm) and Q ( µm) were obtained at the 2.2 m telescope on La Silla, Chile from June 28th to July 02nd, 1997 with the IR array camera MANIAC (Böker et al. 1997). M 17-UC1 was included in an extended survey of M 17 SW covering about and resulting in a mosaic of 133 single frames. Every single frame with a field of view (FOV) of was produced by using chopping techniques with a chopper throw of and its direction set to , parallel to the scanning path. Apart from the object frames, also sky frames were taken at the begin and end of an observing run in order to cope with the sky background and to produce proper flats. Frames of infrared standard stars (e.g. IRTF Photometry Manual 1990, Gehrz et al. 1974, Hanner et al. 1984, Tokunaga 1984, Rieke et al. 1985) were taken for calibration purposes resulting in an accuracy of 25 % in N and 10 % in Q. The data was reduced and analyzed with MOPSI ¹, which resulted in two maps at N and Q from which the detailed images of M 17-UC1 have been extracted. Their positioning was obtained by superimposing various morphological IR features (in particular the Arc as introduced by FJC) with the corresponding structures of the VLA map. From this procedure we can rule out almost any misalignment and estimate the position to be accurate by about .

The VLA observations were carried out on January 15th, 1999 in the C configuration at a wavelength of 1.3 cm. The HPBW of the synthesized beam is ; the fit to M 17-UC1 yields , indicating that the source size is smaller than . The statistical errors of the flux calibration are below 1 %, the absolute uncertainty is 5%. Data reduction was performed with the AIPS software package.

As described in detail in Sect. 3, our MIR maps not only show M 17-UC1 but also another source orientated southwest from it which we call IRS 5S. The photometric results of these two sources are summarized in Table 1.

Table 1. Photometry of M 17-UC1 and IRS 5S.

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000
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